Originally posted by metalmania 10 digits is too much. Do you really think your CC number is safe after that?
The first 10 digits of most credit cards identify bank specific card details and are readily available, even online (the first six are the bank and the last designate other information - google 'credit card bin numbers' if you want to see for yourself!). The last 6 digits are typically the only unique numbers, along with the CVV code on the back of the card (so technically 9 unique digits, along with the expiration date).